Abstract
The dielectric properties of the Ni1-xCaxFe2O4 nanoparticles (x = 0.02, 0.04, and 0.1) synthesized by the citrate precursor method and sintered at two different temperatures, 600 °C and 1000 °C, were investigated by using a complex impedance technique in the range of 100 Hz to 5 MHz. Also, the temperature effect of the dielectric properties of the two sintered Ni0.9Ca0.1Fe2O4 samples at different frequencies was studied in the range of 313 K–773 K showing their semiconducting nature. The frequency dispersion of ε′, ε" and tanδ for all the samples is attributed to the interfacial polarization mechanism, which follows the Maxwell-Wagner model. The variation of the ac conduction in the samples depends primarily on the electron hopping between Fe3+↔Fe2+ ions and hole hopping between Ni2+↔Ni3+ ions in the octahedral sites. The Cole-Cole (Zʺ vs. Zʹ) plots characterize by two overlapping semicircles represented by an electrical circuit consisting of two parallel R–C in series, manifesting the grain and grain boundary effect on the electrical properties of the samples. The (Mʺ vs. Mʹ) plots insure the electric stiffness behavior of this type of ferrites. Moreover, in the present ferrite samples, the lower values of the σʹac, ε′, εʺ, and tanδ at high frequencies, make them suitable for use as an inductor-core for high-frequency power transformers for telecommunication purposes.
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